Coronary artery bypass grafting (CABG) has traditionally been performed with the use of a cardiopulmonary bypass (CPB) machine to oxygenate and perfuse the body during surgery. Recently, techniques have been developed to allow for performing CABG without the use of CPB by stabilizing the epicardial surface of a beating heart at the coronary anastomotic site with a stabilizer (e.g., stabilizing feet) to allow placement of sutures through the graft vessel and recipient coronary artery. This procedure may be performed through a partial or full sternotomy, or via a thoracotomy (which is an incision between two adjacent ribs).
Access to the left anterior descending (LAD) coronary artery is easily performed by either a sternotomy or a thoracotomy. However, the patient typically requires bypass to multiple coronary arteries, including the circumflex artery (CxA) on the left lateral aspect of the heart, the right coronary artery (RCA) on the right lateral aspect of the heart, and the posterior descending artery (PDA) on the back side of the heart. It is very difficult to access the CxA, RCA, and PDA without a sternotomy, as the heart needs to be turned or tilted (or turned and tilted) significantly to reach its side or back, and with an intact sternum, insufficient space exists for these maneuvers. For example, the apex of the heart is generally lifted out of the body through a sternotomy in order to reach the PDA. Surgeons often place the patient in a Trendelenberg position, with the operating table tilted so that the patient's head lies lower than the feet with the patient in supine position, in order to assist with lifting the heart up and back.
An additional challenge to beating heart surgery is that some hearts do not tolerate manipulation well from a hemodynamic standpoint. The potential exists with current manipulation techniques to compress the heart (e.g., by pressing it with stabilization feet) or great vessels (aorta or vena cava) in such a way that hemodynamic function is compromised.
There is a need for a beating heart retraction apparatus capable of physically translating a beating heart from its natural resting place to a location better suited to surgical access, and then holding the beating heart in the latter location during surgery without compressing (or otherwise deforming) the heart or great vessels in such a way that hemodynamic function is compromised.
Typically, beating heart surgery may be accomplished through a partial or full sternotomy using pericardial sutures to retract the heart (outward toward the open sternotomy) into the proper position for surgery, and using a stabilization apparatus (e.g., stabilizing feet) to stabilize the portion of the heart surface to be cut. Sometimes, surgery is performed on the properly positioned heart without using a stabilization apparatus. Before the heart is retracted, a sternal retractor (e.g., sternal retractor 4 of FIG. 1 or sternal retractor 34 of FIG. 2) is positioned to hold the sternotomy incision open, pericardium 1 is then incised along its anterior aspect, and sutures 2 are then placed in the cut edges of the pericardium (as shown in FIG. 2). In FIG. 2, sternal retractor 34 (which is a variation on sternal retractor 4 of FIG. 1) holds the sternotomy incision open. Sutures 2 are then tensioned to expose the heart and to cause the pericardium to lift the heart (as also shown in FIG. 2), thereby retracting the heart. For increased lift (e.g., to attain sufficient lift to access the posterior aspect of the heart), the sutures are often placed deep in the posterior portion of the pericardium.
A disadvantage of piercing through the pericardium in its posterior aspect (with a needle) to place deep sutures is that the pleura (identified by reference numeral 21 in FIG. 3 to be discussed below) is typically also pierced by the needle. The pleura houses the lungs on each side of the mediastinum (which contains the heart) and lies in apposition to the pericardium. Anteriorly, the pericardial surface is free; laterally, it lies against the pleura. When the pleura is punctured, air enters into the pleural cavity and the lungs collapse. At the end of the bypass procedure, bilateral chest tubes must be placed in the chest, and suction used for one or more days to maintain the lungs in an inflated condition. The chest tubes are uncomfortable, painful to remove, and restrict patient ambulation, which is important to early postsurgical recovery.
Conventional use of pericardial sutures for retraction of a beating heart has other limitations and disadvantages including the following. It is inconvenient and potentially harmful to the patient to incise the pericardium and insert sutures along cut edges of the pericardium, and then exert tension on the sutures to move the heart together as a unit with the pericardium. When the sutures are pulled to lift the heart (with pericardium), compressive force exerted by the pericardium on at least one side of the heart sometimes constrains cardiac contraction and expansion.
There are three distinct stages involved in preparing an artery (on an organ) for anastomosis:
1. gross manipulation: the organ is physically translated from its natural resting place to a location better suited to surgical access; PA1 2. artery presentation: the target artery on the organ is identified and the position of the organ is finely adjusted so that the target artery is approachable; and PA1 3. artery stabilization: the target artery and surrounding tissues are immobilized, allowing fine surgical techniques on very small features.
The present invention pertains to an improved method and apparatus for retraction (gross movement) of a beating heart into a desired position and orientation to allow surgery to be performed on the heart, without the limitations and disadvantages of conventional use of pericardial sutures to retract a heart for surgery.